System for producing high-frequency currents.



B. GIRARDEAU & J. BBTHENOD. SYSTEM FOR PRODUCING HIGH FREQUENCY OURRENTS APPLICATION FILED JUNEL, 1913.

Patented June 23, 19M

UNITED STATES PATENT OFFICE.

EMILE GIRARDEAU AND JOSEPH BETHENOID, OF PARIS, FRANCE.

SYSTEM FOR PRODUCING HIGH-FREQUENCY CURRENTS.

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Application filed June 4; 19-13.

To all whom it may concern:

Be it known that we, EMILE GIRARDEAU and JosnPI-r BETHENOD, citizens of the Republic of France, and residing at 128 Rue La Botie, Paris, France, have invented new and useful Improvements in or Relating to Systems for Producing High- Frequency Currents.

For some years past, the development of wireless telegraphy and telephony has been more especially in connection with systems using continuous trains of high frequency waves. Consequently, numerous systems of producing high frequency currents have been proposed, as for instance, Mr. Alexanderson of the General Electric Company having developed special high frequency alternators. Such machines are, however, either very expensive in proportion to the output or must be run at an exceedingly high speed in order that a frequency suitable for wireless apparatus may be attained. It is also known that high frequency currents may be produced by the use of arcs or sparks when the are or spark gap is connected to a suitable circuit, such, for instance, as one containing considerable inductance and capacity connected across the terminals of the are or spark gaps. In all of these latter systems it has been necessary to put between the discharge gaps and the source of current an ohmic resistance of a somewhat important value, whose purpose is principally to prevent putting the source in short circuit when the are or spark is produced. The existence of this resistance'results in the diminution of the overall electric plant efiiciency, as it takes a very important part of the energy provided by the source (50% for example), Whatever may be the efficiency of the initial source of electric energy.

As the above mentioned ohmic loss be comes very serious in large plants serving, for instance, wireless telegraphyor telephony installations the principal object of our invention is to provide a system which will avoid such loss, but which retains'the advantageous feature. of producing the high frequency oscillations by means of a spark a g 2 further object of our invention resides in the particular arrangement and combination of parts hereinafter described.

In the accompanying drawing :Figure 1 is a diagrammatic View of a simple system embodying our invention. Fig. 2 is a dia- Specification of Letters Patent.

Patented June 23, 1914;

Serial No. 771,743.

grammatic View of a somewhat more complicated system than that shown in Fig. 1 but also embodying our invention. Fig. 3 1s a dia rammatic view of a third system also embddy ing our invention, but somewhat more complicated than the system shown in condenser O are shown connected in series across the gap E, the gap together with the -capac1ty and inductance forming an oscillatory circuit for producing high frequency current. Hereafter we shall frequently refer to the circuit E. C. L. in which the energy is used as a discharge circuit. second wire of the supply circuit is shown as connected to an inductance S from which :it leads to the other side of the discharge gap. It will be understood that inductances such as S are commonly connected between the discharge circuit or discharge-gap and the supply circuit in order to prevent high frequency oscillations from passing into the supply circuit. Now assuming that the supply circuit Q is connected to a continuous current source, as soon as the discharge gap breaks down and current passes through the motor M a counter electro-motive force will be generated which acts as a real ohmic resistance. Owing to the unsaturated character of the field of the motor as above described, it will possess also a certain inductance. This inductance is, however, not at all prejudicial as it enables us to reduce the value of the self-inductance S which is usually necessary for the purpose above Eis The

mentioned. As the machine M acts as a mosuggested. In this figure we have combined th motor M with the generating dynamo, so' that both of the machines have the same armature, thus saving a collector or commutator. In this figure the discharge circuit E, C. L. remains as before and is connected on one side to the inductance S to the commutator of machine M and on the other side is connected to the commutator of the machine M through the demagnetizing field winding 7 The armature of the machine is indicated as I and we have provided a separate exciting circuit, the means of which are indicated by plus and minus, respectively, and connected-across which is a field coil W and a variable resistance R similar to that usually placed in series with the fields of generators. It will be seen in this arrangement that the demagnetizing series winding W assumes the same function as the series motor M in the arrangement of Fig. 1, while the whole set serves as a proper generator. that the current supplied to the discharge circuit is of a continuous character. It will 'be understood also in connection with the arrangement of Fig. 2 that while continuous current generators have previously been used with demagnetizin series field windings that such uses have een in combination entirely different from the present one. It will be understood, moreover, that in the present application the proportion between the ampere turns in the fields W and W is important as it is necessary that the ampere turns of the winding W be a very important fraction of the ampere turns of the winding W Referring more particularly to Fig. 3, we have here shown a system which is particularly designed for use with large plants. In this arrangement the armature is a machine and is excited by a coil W while the discharge circuit E. L. O. and the inductance S is as before. In this arrangement, however, the excitation .for the machine M is furnished by a special exciter Z the commutator of which is connected to the opposite ends of the winding W. The coil W is placed in the field of the exciter Z being connected into the armature circuit of the machine M between the commutator thereof and the discharge circuit and is so arranged as to demagnetize the field of the machine Z. The exciter Z is provided also with a field winding W by which its electro-motive force is ordinarily built up so as to bring that of the machine M up to the point where it can produce a discharge across the gap E. Theends of the winding W are connected to any convenient source of continuous current and the usual regulating rheostat R is shown connected in series therewith. It will be noted, however, that when the discharge circuit is supplied from a, source of constant It will be seen in this case also voltage through an ohmic resistance that the voltage supplied to the discharge circuit is decreased in exact proportion to the current being used. Thus if the voltage available at the terminals of the discharge circuit be represented by Z, the voltage of the source by E and the current in the circuit by J, then Z is equal to E KJ, where K is a constant.

Sinc the winding 1V possesses necessarily a considerable self inductance, the current therein will not vary immediately as the field varies and consequently the operation of the system would not be as satisfactory as one using an ohmic resistance unless means were provided for overcoming the effects of self inductance. With this end in view we provide a current transformer T the primary of which is connected in series with the armature of the machine M and the coil W so that it will eceive the current of the main circuit. The secondary of the transformer T is connected in the armature circuit of the machine Z between said machine and the coil W in such a manner that when there is a, sudden rush of current through the main circuit, there will be an electro-motive force generated in the secondary coil of the transformer T which opposes the normal electro-motive force of the machine Z and consequently has the effect of overcoming the result of the self inductance of the coil W. By suitably proportioning the various coils in winding we thus produce a system in which the voltage drop at the terminals of the machine M is directly proportional to the amount of current flow and indeed this result may be demonstrated by certain theoretical considerations which may be expressed mathematically, but which it is believed not to be necessary to set forth.

It will be understood, however, that while we have shown and described the preferred form of our invention, that Various electrically equivalent elements may be substituted for the parts of the system herein described in proportion to the quantity of current being supplied thereto.

2. The combination with a discharge circuit for producing high frequency oscillation, of an armature for supplying current to said circuit, and a coil for coacting with said armature, said coil connected in series with said discharge circuit and so arranged in conjunction with said armature as to decrease the electromotive force of the supi' ture, an exciter armature for supplying current to said field coil, means for exciting said eXcit-er armature, a field coil for said exciter armature connected in series with said discharge circuit and said first men- 3. The combination of a discharge cirtioned armature which is so arranged as to oppose the normal excitation of said exciter armature when current is flowing into said discharge circuit, and a current transformer the primary of which is connected in series with said discharge circuit, said first mentioned armature and said coil and the secondary of which is connected in series to said field winding and said exciter armature, said current transformer being so connected that it opposes the effect of self inductance in said field winding.

In testimony whereof we aflix our signatures in presence of two witnesses.

EMILE GIRARDEAU. JOSEPH BETHENOD. Witnesses:

JOHN BAKER, JACK H. BAKER. 

